So Palka, 33, made a documentary that follows her decision to be tested to see if she has the gene for Huntington’s. The diagnosis is definitive, so there is no turning back.

Her film, “The Lion’s Mouth Opens,” directed by Lucy Walker ("Waste Land,” 2010), is screening around the country and has been short-listed for an Academy Award in the documentary short-subject category. It will debut on HBO this spring.

Palka watched the deterioration of her own father, once a “charismatic intellectual,” who is now in the late stages of the disease — “a living ghost” at a nursing home in Scotland. Two of his siblings also had the hereditary disease.

“If you have ever lived with someone or had a parent with Huntington’s the last thing you want to do is walk into a room and get tested,” she told NBC News. “You know the nightmarish reality of going into dementia. It’s like being in a war zone — like being sent back to Iraq with PTSD.”

Some with rare diseases like Huntington’s choose not to be tested if there are no medical interventions. Of the 7,000 rare diseases, only 350 have therapies approved by the Food and Drug Administration, according to the National Organization for Rare Disorders (NORD).

But others, like Palka, want to know.

“There are many people … who just want to be able to put a name on their disease,” NORD spokeswoman Mary Dunkle told NBC News. “We even have parents of children with a terrible disease who have said to us after getting a diagnosis, that it’s a relief.”

“There are many people … who just want to be able to put a name on their disease."

An estimated 30,000 Americans live with Huntington’s, a disease that affects their ability to walk, to think and to regulate their mood. But an even larger group — about 250,000 — are at risk, but symptom-free.

In 1983, scientists discovered a genetic marker on chromosome 4, which led a decade later to isolation of the gene. Today, a direct genetic test for the disease is available at 20 centers around the United States.

"Typically, the decision comes when young couples think about planning a family,” said Louise Vetter, CEO of the Huntington’s Disease Society of America (HDSA). “It takes a proactive and special kind of person to say they are prepared for whatever they learn and know they can handle this.”

Palka, who works closely with HDSA, said only about 10 percent of all those who are at risk but symptom-free choose to get tested.

But Palka is buoyed by new medical research that provides hope for those with Huntington’s. “It’s a magical time,” she said.

HDSA has spent $18 million on global research since 1999. Scientists at Washington University can now take a tiny piece of flesh from the forearm to make neurons to replace dying ones in the brain. And other research to find an “off switch” for the progression of Huntington’s disease shows promise.

Palka has become an activist supporting legislative efforts to fight discrimination and to secure equal rights to medical and disability benefits in a Parity Act.

Her film title refers to the Bob Dylan poem "Last Thoughts," written after he visited folk singer Woody Guthrie, who died in 1967 of Huntington's disease: "And the lion's mouth opens and y'er staring at his teeth, and his jaws start closin' with you underneath.”

Since she was 13, Palka has been able to recite the Dylan poem by heart.

“He describes it so well,” she said. “He was talking about someone going crazy — when we’ve lost our minds. It’s about not having control over what’s happening to you.”

“I would never tell anyone to do what I did."

The results of Palka’s genetic test won’t be revealed here, but she has embraced a holistic nutritional program, avoids environmental toxins and participates in body-mind practices like yoga and meditation.

“Genes are malleable,” she said, adding that she is working to keep her body “stress-free and in healthy state.”

As for recommending that others take her path and get tested, Palka said, “I don’t think it’s a good idea.”

She said some who test positive go on to suffer depression or kill themselves. “I would never tell anyone to do what I did,” she said.

“It’s such a hall of mirrors,” said Palka. “I guess it’s a good thing to face things that are difficult, but you have to have a support system in place and know that it is the right thing for you and don’t just do it for other people.”

And if someone does get tested, Palka said she should be surrounded by family and friends. “No one should be alone to hear news like that.”

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